Based on the number of people alone, the country that has the most Christians is the United States, with more than 200 million people, or more than 65 percent of the U.S. population, identifying themselves as Christian. In terms of percentage of population, the Vatican and the Pitcairn Islands are the most Christian countries, with both estimated to be 100 percent Christian.
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China has a rapidly growing Christian population, with about 55 million Christians — more than 5 million more than there are in Italy.
There are thought to be more than 2 billion Christians worldwide, with almost 40,000 denominations. The largest denomination in terms of people is Roman Catholic, with more than 1 billion adherents.
Brazil, Russia and Mexico are the countries with the next-largest numbers of Christians, though when calculated by percentage, Ecuador, Armenia, American Samoa and Greece all have more than 98 percent of their population identifying themselves as Christian.
Countries with the lowest percentage of Christians in the population include Somalia, which has about 0.01 percent of its population identified as Christian; Yemen, with a little more than 0.01 percent; and Afghanistan, with about 0.02 percent.